(1) Field of the Invention
This invention relates to producing oil wells, and more particularly to wells having reciprocating pumps operating from the surface by sucker rods.
(2) Description of the Prior Art
Pumping oil wells with a reciprocating pump at the bottom of the well and a sucker rod extending through an eduction tube is old and well know.
Traditionally, a sucker rod string was composed of a series of metal rods about 25 to 30 feet long, having a male or threaded pin connection at each end. They were connected together by cuffs, i.e., a coupling having a female or internally threaded cup at both ends.
In recent years, there has been considerable use of synthetic materials such as fiberglass rods. These strings are often several hundred feet long. It has been found that with the use of fiberglass rods that it is necessary or essential that they never be permitted to come under compression loads while in use. Therefore, it is necessary when using the fiberglass rods, because of their light weight, to attach sinker barsat the lower end of the sucker rod string. These sinker bars are normally joints about 25 to 30 feet long having a square or cylindrical cross section and a threaded pin or box connection on each end.
The couplings or cups by which the sinker bars are connected have a cylindrical configuration with the diameter of the cylindrical configuration greater than the diagonal width of diameter of the square or cylindrical sinker bar cross section. Therefore, the sinker bars themselves would not contact the eduction tube but would normally be held away from contact with the eductiontube by the couplings.
Often times, the pump is far below the surface of the earth, e.g., 5,000 feet. Normally, standard size eduction tubs are used having standard internal diameters. However, those familiar with oil field operation will understand that often, because of rough treatment or otherwise, that not every joint of the eduction tube will be cylindrical throughout its length and of uniform inside diameter. Therefore, to physically insert a cylindrical element through the tube, it must be of somewhat smaller diameter than the internal diameter of an "undamaged" eduction tube.
It will be understood that the eduction tube is often not vertically straight. Often, because of drilling, it will have bends, curves, or corkscrews in it. So, normally the coupling would keep the sinker bar from contact with the eduction tube. The couplings are flexible to bend in a crooked eduction tube because the sinker bars cannot bend enough.
However, the sucker rod would not be axially aligned with the eduction tube. This causes problems particularly at the pump. The pump and the plunger of the pump is by necessity held in axial alignment with the eduction tube. If the sucker rod above the pump is not axially aligned, there is a problem of excessive wear at points of contact and at the pump, which is an existing problem in the industry.
In addition, there is always the possibility that threaded connections become unthreaded and the sucker rod string parted for this reason; i.e., sometimes the sucker rod string or elements of it break apart. In such cases it is necessary to "fish" the parts from the well.
Before this application was filed, the applicant caused a search to be made in the U.S. Patent and Trademark Office. The following patents were found on that search:
______________________________________ FILING ISSUE NUM- NAME DATE DATE BER ______________________________________ KINNY Jul. 5, 1932 Jul. 28, 1936 2,049,265 PARAMORE ET AL. May 4, 1981 Feb. 14, 1984 4,430,787 SABLE May 18, 1966 Dec. 3, 1968 3,414,337 JEVNING - Jun. 10, 1967 Dec. 3, 1968 800,390 CANADIAN SMITH Oct. 3, 1949 Sept. 15, 1953 2,652,231 MORRIS Dec. 18, 1968 Feb. 2, 1971 3,560,060 COLLETT Jan. 30, 1968 Jan. 20, 1970 3,490,526 WILLIAMS Feb. 28, 1938 Sep. 12, 1939 2,172,602 PRIDY Aug. 25, 1980 May 11, 1982 4,329,124 SOULIE ET AL. Feb. 11, 1971 Oct. 10, 1972 3,697,104 BURGE Mar. 19, 1982 Aug. 28, 1984 4,467,879 KNUTSEN Oct. 6, 1981 May 31, 1983 4,385,669 BOICE Jul. 5, 1946 Dec. 29, 1953 2,664,272 ______________________________________
KINNY discloses a sucker rod coupling having a bearing made of stellite.
PARAMORE ET AL., SABLE, JEVNING, SMITH, MORRIS, and COLLETT all describe sucker rods with guides or centralizers or the like.
WILLIAMS, PRIDY, SOULIE ET AL., BURGE, KNUTSEN, and BOICE are included herewith only because the applicant believes the Examiner would consider anything revealed by an experienced patent searcher to be relevant and pertinent to the examination of this application.